I’m not sure why you feel its fragmented – the game introduces you to the passive point system and the skill point trees fluidly. The stats page tells you what each does, and the in game guide goes into more specifics (though I feel like the guide could be put together a little bit better). The hard thing about loot is that unless the game knows exactly what you’re build is trying to do (which is basically impossible) its really hard to tell you whether or not one piece of gear is better than the other. Personally, I don’t want to just have a “DPS better, Defense better, therefore item is better” kind of breakdown. We should have to put effort into understanding what makes our characters better.
The crafting system is introduced in a quest, (its been a while) but I believe it introduces you to each unique system in the crafting system itself as well. As far as loot filters are concerned, they are a relatively new addition to the game with many requested features. I personally don’t play with one and it tends to work out for me. They’re not necessarily needed, but I can understand the want for them. You can certainly make a generic loot filter @Heavy has very nice ones here ( [0.9.2] Heavy'z Casual Loot Filters for all Classes v3.1 ), but loot filters also suffer from the fact that you need to know what is going to make your character better. Some characters may want Fire damage affixes while others may want Cold damage affixes.
You most certainly do not NEED to research viable builds – almost everything is viable in this game, unless you’re doing something incredibly wacky, you would be hard pressed not to be able to put together a set of 5 skills that couldn’t be viable. Though, the meaning for what’s viable is kind of left up to debate right now. Personally, I take enjoyment from making my own builds and trying different things out, and the fact that it will likely be viable in end game content (at least, how the game stands now) is nice. I guess what I’m saying is free yourself from the notion that only other people that make guides can make viable builds, you can do it too.
As I’m sure you can tell, there is no huge passive skill tree in this game. Each skill gets its own skill tree, which is relatively small and manageable. What else they add to the game later on, who’s to say what that will look like, but I imagine a mix of new content/systems will emerge, but it will certainly be different than what’s seen in POE, the devs have shown that they’re committed to making THEIR game.
I absolutely do not want there to be a solo mode with better loot drops and faster leveling. Maybe a mode that’s an adventure mode like D3 for leveling, that could be faster, but not because it the mode itself offers an experience buff. Again, just to reiterate, you can level with almost anything you wish – there’s no need to “know” builds.
Not to sound to facetious, but D3 does exist already … But I imagine many (and potentially you) don’t play it for the same reason I don’t, there’s not much thought you have to put into progressing your character. Unplugging your brain can happen in this game too, just like any other game, you’ll eventually have things memorized/know what you’re looking for or what your plan is ( you can plan builds here Last Epoch Build Planner) before you start playing.